My fave way is to roast lots of vegetables. I love butternut squash, carrots, red, green and yellow peppers, courgettes, beetroot, fennel and tomatoes. I do this at least 2 x a week and there's always leftovers for lunches etc. I also love baked cauliflower with cumin; sprinkle cauliflower florets with salt, pepper and a generous amount of ground cumin and bake at 200C for 20 minutes. Its delicious!
I also make steamed broccoli, green beans, pak choi and make a lot of stir fries with rainbow stir fry veggies, okra etc. Braised cabbage also tastes great especially with a steak. You could also start each main meal with a bowl of vegetable soup made of superfree veggies!